The chapter evaluates how the EU's legal obligation to promote the rule of law affects the EU's perspective on international investment law. Against the backdrop of the ongoing investment law reform process, the chapter discusses the question with what authority the European rule of law demands such reforms. The chapter addresses both international investment law's conceptual deficits with respect to the rule of law and aims to demonstrate that the EU's reform efforts to bring international investment law more in line with the rule of law do not only follow a political agenda, but are also determined by the EU's legal binding obligation to promote the rule of law.